Coaxial switches of various design have been used for many years and are well known in the art. Such coaxial switches are useful in applications where extremely high frequency signals are to be coupled or routed from one transmission line to another. The major problems encountered in the design of coaxial switches have typically been to maintain a uniform impedance characteristic over the length of the transmission line through the switch, while at the same time maintaining good electrical contact. Abrupt changes in these characteristics cause signal reflections and changes in the voltage standing wave ratio, and these problems are compounded as the frequencies increase.
One coaxial switch capable of both double pole, double throw and single pole, multiple throw configurations is taught by U.S. Pat. No. 2,697,767. The center conductor of a transmission line is disposed in an open cavity in a rotor such that the matching face of the associated body forms a portion of the outer conductor. A plunger assembly inside the rotor bears on the center conductor to maintain good electrical contact. In other words, room is provided within a surrounding dielectric block to permit the center conductor to move under spring pressure. This arrangement results in unwanted reflections generated at the point where the plunger bears on the center conductor. In addition, the dielectric constants of the transmission line are uneven, resulting in a non-uniform and unpredictable impedance characteristic over the length of the transmission line.